1. Field of the Invention
The present invention pertains to turf reinforcement mats.
2. Background Art
Turf reinforcement mats (xe2x80x9cTRMxe2x80x9d) are now in widespread use. TRM are used to protect the soil surface from severe erosion during high velocity, surface flow conditions, primary applications being channels, ditches, steep-long slopes and river bank stabilization. TRM vary in construction from loosely woven or non-woven plastic mesh to multiple layers of inorganic netting structures, loose filled with organic fibers, all stitched together. The use of plastic mesh or grid-like materials such as colbond, pyramat, enkabond, and others, provide little assistance in seed germination: their principal use is in providing reinforcement of the seed bed once seeds are germinated. By incorporation of such materials, the root systems are able to withstand much greater water velocity in overland flow, (water runoff) conditions. However the open nature of these products does little to reduce sediment and seed displacement prior to seed bed establishment.
Fiber mats have been used to assist seed germination and impair runoff. 100% organic blankets without the inorganic grid component aren""t suitable for turf reinforcement applications. TRM products can take the place of rip rap or concrete for channel applications, an aesthetically attractive alternative while providing permanent long term protection to the channel.
Establishing seed beds in areas where high runoff is expected, i.e. on steep slopes, in gulleys, drainage channels, etc., has often required separate use of one or the aforementioned synthetic polymer grid-like materials and a separately applied fiber mat. Such a two-step approach is time and labor intensive, however, and has not been in widespread commercial use.
In U.S. Pat. No. 5,849,645, a complex composite mat having a heavy gauge bottom polymer grid, a heavy gauge top polymer grid, and a xe2x80x9ccuspatedxe2x80x9d (pleated) xe2x80x9csuper heavyxe2x80x9d gauge polymer netting are combined with a fiber matrix of coconut fibers to form a multilayer assembly which is stitched together to form an integral, multilayer composite structure. This product is widely used, and offers both runoff protection, assistance in seed germination, and protection against runoff in established seed beds. However, the product is expensive to manufacture and adds large quantities of substantially non-biodegradable materials to the soil due to its construction which necessarily contains three polymeric layers.
It would be desirable to provide a TRM product which offers runoff protection, assistance in germination, and protection against runoff in established seed beds, which introduces less synthetic polymer material into the soil and which can be inexpensively manufactured.
It has now been surprisingly discovered that a lofty synthetic polymer grid or non-woven can be economically combined with a fibrous mat to form a lofty TRM product. The polymer grid protrudes from at least one side of the composite product, and the product is installed with an exposed grid side toward the soil. In a particularly preferred embodiment, the fibrous mat contains minimally 5 weight percent of a low melt synthetic fiber and is thermally bonded to the lofty polymer grid.